However, there is no particular reason for the C species to reside in the interstitial lattice.
Contrasts are also assumed for Si$_{\text{i}}$.
Once precipitation occurs, regions of dark contrasts disappear in favor of Moir\'e patterns indicating 3C-SiC in c-Si due to the mismatch in the lattice constant.
-Until then, however, these regions are either composed of stretched coherent SiC and interstitials or of already contracted incoherent SiC surrounded by Si and interstitials, where the latter is too small to be detected in HREM.
+Until then, however, these regions could either be composed of stretched coherent SiC and interstitials or of already contracted incoherent SiC surrounded by Si and interstitials, where the latter is too small to be detected in HREM.
In both cases Si$_{\text{i}}$ might be attributed a third role, which is the partial compensation of tensile strain that is present either in the stretched SiC or at the interface of the contracted SiC and the Si host.
Furthermore, the experimentally observed alignment of the \hkl(h k l) planes of the precipitate and the substrate is satisfied by the mechanism of successive positioning of C$_{\text{s}}$.
In addition, sharper peaks in the radial distribution functions lead to the assumption of expeditious structural formation.
The increase in temperature leads to the occupation of new defect states, which is particularly evident but not limited to the low C concentration simulations.
-% todo - cut-off effect increases for non-equilibrium processes, thus, to mimic IBS increased temperatures are exceptionally necessary
The question remains, whether these states are only occupied due to the additional supply of kinetic energy and, thus, have to be considered unnatural for temperatures applied in IBS or whether the increase in temperature indeed enables infrequent transitions to occur faster, thus, leading to the intended acceleration of the dynamics and weakening of the unphysical quirks inherent to the potential.
As already pointed out in section~\ref{section:defects:noneq_process_01} and section~\ref{section:defects:noneq_process_02}, IBS is a non-equilibrium process, which might result in the formation of the thermodynamically less stable \cs{} and \si{} configuration.
Indeed, 3C-SiC is metastable and if not fabricated by IBS requires strong deviation from equilibrium and low temperatures to stabilize the 3C polytype.
This is in fact found to be favorable in the absence of the \si{}, which turned out to have a low interaction capture radius with the \cs{} atom and very likely prevents the recombination into a thermodynamically stable \ci{} DB for appropriate separations of the defect pair.
Results gained in this chapter show preferential occupation of Si lattice sites by \cs{} enabled by increased temperatures supporting the assumptions drawn from the defect studies of the last chapter.
-Moreover, the cut-off effect as detailed in section~\ref{section:md:limit} is particularly significant for non-equilibrium processes.
+Moreover, the cut-off effect as detailed in section~\ref{section:md:limit} is particularly significant for configurations that are deviated to a great extent from their equilibrium structures.
Thus, for instance, it is not surprising that short range potentials show overestimated melting temperatures while properties of structures that are only slightly deviated from equilibrium are well described.
Due to this, increased temperatures are considered exceptionally necessary for modeling non-equilibrium processes and structures such as IBS and 3C-SiC.
\section{Long time scale simulations at maximum temperature}
As discussed in section~\ref{section:md:limit} and~\ref{section:md:inct} a further increase of the system temperature might help to overcome limitations of the short range potential and accelerate the dynamics involved in structural evolution.
-Furthermore these results indicate that increased temperatures are necessary to drive the system out of equilibrium enabling conditions needed for the formation of a metastable cubic polytype of SiC.
+Furthermore, these results indicate that increased temperatures are necessary to drive the system out of equilibrium enabling conditions needed for the formation of a metastable cubic polytype of SiC.
A maximum temperature to avoid melting is determined in section \ref{section:md:tval} to be 120 \% of the Si melting point but due to defects lowering the transition point a maximum temperature of 95 \% of the Si melting temperature is considered usefull.
This value is almost equal to the temperature of $2050\,^{\circ}\mathrm{C}$ already used in former simulations.
Furthermore, C implanted at room temperature was found to be able to migrate towards the surface and form C-rich clusters in contrast to implantations at elevated temperatures, which form stable epitaxially aligned 3C-SiC precipitates \cite{serre95}.
In simulation, low temperatures result in configurations of highly mobile \ci{} \hkl<1 0 0> DBs whereas elevated temperatures show configurations of \cs{}, which constitute an extremely stable configuration that is unlikely to migrate.
Indeed, in the optimized recipe to form 3C-SiC by IBS \cite{lindner99}, elevated temperatures are used to improve the epitaxial orientation together with a low temperature implant to destroy stable SiC nanocrystals at the interface, which are unable to migrate during thermal annealing resulting in a rough surface.
-Furtermore, the improvement of the epitaxial orientation of the precipitate with increasing temperature in experiment perfectly conforms to the increasing occurrence of \cs{} in simulation.
+Furthermore, the improvement of the epitaxial orientation of the precipitate with increasing temperature in experiment perfectly conforms to the increasing occurrence of \cs{} in simulation.
+%
+% todo add sync here starting from werner96 (Similar, implan ...)
+%
At elevated temperatures, implanted C is therefore expected to occupy substitutionally usual Si lattice sites right from the start.
Thus, elevated temperatures are considered to constitute a necessary condition to deviate the system from equilibrium, as it is the case in IBS.
However, agglomeration and rearrangement is enabled by mobile C$_{\text{i}}$, which has to be present at the same time and is formed by recombination of C$_{\text{s}}$ and Si$_{\text{i}}$.
Indeed, \si{} is observed in the direct surrounding of the stretched SiC structures.
Next to the rearrangement, \si{} is required as a supply for additional C atoms to form further SiC and to compensate strain, either within the coherent and stretched SiC structure as well as at the interface of the incoherent SiC precipitate and the Si host.
+%
In contrast to assumptions of an abrupt precipitation of an agglomerate of C$_{\text{i}}$ \cite{werner96,werner97,eichhorn99,lindner99_2,koegler03}, however, structural evolution is believed to occur by a successive occupation of usual Si lattice sites with substitutional C.
This mechanism satisfies the experimentally observed alignment of the \hkl(h k l) planes of the precipitate and the substrate, whereas there is no obvious reason for the topotactic orientation of an agglomerate consisting exclusively of C-Si dimers, which would necessarily involve a much more profound change in structure for the transition into SiC.
-\chapter{List of publications}
+\addcontentsline{toc}{chapter}{List of publications}
+\bibliographypub{../../bibdb/bibdb}{}
+\bibliographystylepub{thesispub}
- \section{Papers}
+% own publications
+\nocitepub{zirkelbach11,zirkelbach10,zirkelbach09}
+\nocitepub{zirkelbach2007,zirkelbach2006,zirkelbach2005}
- \begin{enumerate}
- \selectlanguage{german}
- \item F. Zirkelbach, M. H"aberlen, J. K. N. Lindner, B. Stritzker.\\
- \selectlanguage{english}
- {\em Modelling of a selforganization process leading to periodic arrays of nanometric amorphous precipitates by ion irradiation.}\\
- Comp. Mater. Sci. 33 (2005) 310.
- \selectlanguage{german}
- \item F. Zirkelbach, M. H"aberlen, J. K. N. Lindner, B. Stritzker.\\
- \selectlanguage{english}
- {\em Monte-Carlo-Simulation study of the selforganization of nanometric amorphous precipitates in regular arrays during ion irradiation.}\\
- Nucl. Instr. and Meth. B 242 (2006) 679.
- \end{enumerate}
-
- \section{Conference talks}
- \begin{enumerate}
- \selectlanguage{german}
- \item F. Zirkelbach, M. H"aberlen, J. K. N. Lindner und B. Stritzker.\\
- {\em Monte-Carlo-Simulation der Selbstorganisation amorpher nanometrischer $SiC_x$"=Ausscheidungen in Silizium w"ahrend $C^+$-Ionen-Implantation}\\
- AKF-Fr"uhjahrstagung der DPG, Regensburg, 2/2004, DS 1.4
- \item F. Zirkelbach, M. H"aberlen, J. K. N. Lindner und B. Stritzker.\\
- {\em Kinetik des Selbstorganisationsvorganges bei der Bildung von $SiC_x$"=Ausscheidungs-Arrays in $C^+$-Ionen-implantiertem Silizium.}\\
- 69. Jahrestagung der DPG, Berlin, 2/2005, DS 8.6
- \selectlanguage{english}
- \end{enumerate}
-
- \section{Diploma thesis}
- \selectlanguage{german}
- {\em Monte-Carlo-Simulation von selbstorganisierten nanometrischen $SiC_x$"=Ausscheidungen in $C^+$"=implantierten Silizium}.
- \selectlanguage{english}
+%\renewcommand\bibname{List of publications}
projects / lectures / latex.git / commitdiff